PHOENIX -- Members of the public can exchange unwanted firearms for grocery store gift cards at three gun buyback events this month.

Arizonans for Gun Safety, the Phoenix Police Department and Mayor Greg Stanton are collaborating on what they say is the largest "Groceries for Guns" exchange in the state's history.

The buyback events are May 4, 11 and 18 from 10 a.m. to 2 p.m. or until all the gift cards are gone. The three locations are Southminster Presbyterian, 1923 E. Broadway Road; Betania Presbyterian, 2811 N. 39th Ave.; and Sunnyslope Mennonite Church, 9835 N. Seventh St.

Those exchanging handguns, shotguns or rifles will receive a $100 Bashas' gift card per gun and those exchanging assault weapons will receive a $200 gift card per gun. The gift cards can also be used at Food City and AJ's Fine Foods.

"This is an opportunity for the community to become involved and partner with the Phoenix Police Department in public safety efforts," Chief of Police Daniel V. Garcia said. In addition, "these events offer a viable option for people to dispose of their unwanted guns."

Police said the firearms can be turned in anonymously -- no questions asked.

"The gun-buyback program is voluntary, completely up to gun owners to make their own choice about a weapon they may have in their possession," Stanton said in a media release. "If it can even solve one crime or return a gun to its rightful owner, we'll know it's worth it."

Bringing unloaded firearms. (If you cannot unload the weapon, inform the officers when you arrive.)

Before arriving, place the firearm in a trunk, back seat (if no passengers), bed of truck or glove box.

Do not hand the firearm to the officer when you arrive. Instead, officers will get the firearm from one of the listed locations indicated by you.

Buybacks are popular among some police and elected officials who either pay cash or hand out gift cards in exchange for weapons. However, such events face an uncertain future in Arizona after Gov. Jan Brewer signed a bill Monday that requires reselling surrendered weapons instead of destroying them.